1. Field of the Invention
The present invention relates to an error correction encoding system for use in effecting data communication via a fading channel dominated by burst errors in communication among vehicles such as automobiles, etc.
2. Description of the Prior Art
"Error correcting code" to automatically correct digital information is indispensable nowadays to improve reliability of computers and data communication systems. Two types of error encoding systems are known for the error correcting codes. One is suited to random error correction, and the other to burst error correction depending on error patterns to be corrected. In particular, in extremely bad-conditioned channels such for example as fading channels in communication among vehicles such as automobiles, the burst error is dominant. For a system to correct the burst error, an intereleaving system is known as described in "Error Correction Coding Starting to Be Extensively Put into Practice in Various Fields" by Tanaka, Nikkei Electronics, 1975, 12 to 15, pp 48 to 52. This interleaves the burst error, and thereby converts it to a random error which can be then satisfactorily processed with use of proper random error correcting codes. However, the system can not be applied to systems requiring a severe delay time characteristic since the sytem delays in its decoding.
In addition, another error correction system such an automatic repeat request method as being described in Malcolm C. Easton "Bath Throughput Efficiency of ADCCP/HDLC/SDLC Selective Reject Protcols" 1980, TEEE, PP 187 to 195 is known.
Both systems are greatly varied in the burst length because of in a mobile radio, great changes of a vehicle speed ranging from zero to one hundred and several tens of kilometers per hour as well as of a signal reception level ranging from about minus 100 dB to minus several tens of dB. Accordingly, several hundred bits of interleave are needed to randomize a signal with use thereof, whereby more delay time is required. Thus, larger capacity memory of a RAM is needed and further throughput efficiency is deteriorated. In addition, to securely effect communication only with an error correcting code having a burst length of several bits, throughput efficiency is sharply deteriorated.